Circulation system of pulp digesters



P 1944- 1. P. TRQEDSSON 2,359,172

CIRCULATION SYSTEM OF PULP DIGESTERS Filed May 1, 1940 l van PenrgTro Ed 550 n INVENTOR ATTORNEY U Patented Sept. 26, 1944 UNITED STATES PATENT OFFICE CIRCULATION SYSTEM OF PULP DIGESTERS Ivan Penry Trodsson, Tokyo, Japan; vested in Custodian the Alien Proper-t Application May 1, 1940, Serial No. 332,711 In Japan April 20, 1939 2 Claims.

This invention refers to an improvement in circulation systems of pulp digesters at which a forced circulation of the mixture of pulp and liquid in the digester is obtained by means of a. pump, placed in a pipe line connecting the -off strainer from being clogged and choked. by

the chips or the pulp.

The object or the invention is to make it possible to use forced circulation systems when cooking certain raw materials which have such a consistency that circulation by hitherto known arrangements is impossible. One such raw material is, for instance, bagasse. Such raw materials have a tendency to pack hard in the digester, and to form more or less large lumps which are liable to choke the circulation piping and cause the circulation to stop. They may also accumulate on the draw-oil strainer so that it becomes impossible to draw 01! the surplus liquid. The present invention aims at removing operating diinculties of this kind.

The invention is schematically illustrated in vertical section in the attached drawing. in which I indicates the digester, 2 the circulation pump. 3 the suction pipe to the pump 2, 4 the pressure pipe from pump 2, 5 the rotary or oscillating body which is mmmtedon the shait I. and driven, for instance by the pulley 1 or in some applying the invention. It is however possible also to apply the invention at such circulation systems where the circulating cooking liquid is separated from the pulp by means of a strainer placed before the suction pipe to the pump, and at which the practically fibre-free liquid only enters the circulation piping and the pump. At such circulating systems the strainer might gradually become choked with chip and pulp, but

by using the rotary or oscillating body as described above the strainer can be kept clean, so that the circulation will work smoothly.

I claim:

1.'A pulp digester comprising a tank having an upper outlet aperture and a lower inlet aperture, a tube secured to said tank and extending from the outlet aperture to the inlet aperture,

whereby communication is established between the inside of said tank and the inside of said tube, a pump connected with said tube and adapted to draw the contents oi said tank through said outlet aperture into said tube and feed the same through said inlet aperture back into said tank, movable means secured to said 2 tank in proximity to said outlet aperture, said movable means comminuting the contents of the tank drawn into said outlet, and means for actuating said movable means, said tank being provided with a withdrawal aperture disposed above and in proximity to said outlet aperture, a

strainer covering said withdrawal aperture and secured to the inside oi said tank, said strainer being also disposed in proximity to said outlet aperture and said movable means, whereby the movable means simultaneously keeps said strainer unobstructed.

2. A pulp digester comprising a tank for containingamixturesuchasmlpandliquid, means for withdrawing said liquid from the upper porother known way, 8 is the drawing-oi! strainer. tion or said tank under a suction and for torc- The mixture of pulp and cooking liquid is drawnbythepumplviatherotarybodytinto the suction pipe I in the upper Part of the digester, and after passing the pump 2 is returned by way or the pressure pipe into the lower part 01' the digester. The rotating bQdy 5 breaks up any agglomerations of chips or pulp so that the flow into the suction piping becomes smooth and unobstructed. At the same time the rotary body ingthesamebackintothelowerportionoi'the tank under pressure, said tank being provided with an overflow aperture disposed above and in proximity to said point of withdrawal, means for comminuting said mixture at said withdrawal point, filtering means covering said overflow aperture, said filtering means being also disposed in proximity to said'comminutlng'means and said withdrawal point, whereby said comminut- 5 prevents any chips or pulp from settling on ing means will also prevent pulp from accumuthe drawing-oi! strainer I.

The attached drawing shows only one way of lating upon said filtering means.

IVAN PENRY mofinsson. 

